Can't Ping Wireless Laptop?

Yesterday I encountered problem where 2 of my Laptops can't ping each other. The laptops are running Windows XP SP2 and Vista Home Basic SP2. I did remember my laptops can ping each other before but suddenly they give error message "Destination host unreachable". NOTE: Both laptops can ping the router and surf internet with no problem.

At first I thought it was firewall issue and so I turned it off for both laptops. To no luck the problem still there. I then googled for answer and still it didn't get me anywhere, even though others also encountered it and asking for help.

Finally I tried out my own debugging of the matter. Hey, I'm also an I.T. and Engineer guy. So, I should be able to find out the problem. :) In fact I did find the problem and solution to it. It's pretty simple. Problem occured at the router side. Because wireless of both laptops are using DHCP to get its IP address, the router itself needs to keep track of which IP being assigned to which MAC. You need to check your router DHCP table of a list of IP leases. Find which entry in the DHCP table that has "unknown" IP but has MAC address as its correspondent. This is the root of the problem. An invalid entry in DHCP table.

The solution is easy, disconnect wireless connection of the laptop that has "unknown" entry in the DHCP table. Issue command "ipconfig /all" to check your MAC address. Re-connect your wireless, refresh your DHCP table in the router and ensure there is no "unknown" entry anymore in the table. That's it, your problem solved. Happy pinging!

NOTE: your firewall is not an issue. You don't have to turn it off but ensure you allow ping/ICMP as part of your firewall exceptions.